They're also a nightmare for fishermen, who must contend with bursted nets and clogged trawl lines. Japan's now-annual bloom of Nomura jellyfish, which each grow to be the size of large refrigerator, capsized and sank a 10-ton trawler when the fishermen tried to haul up a net full of them.

That's a terrifying image, but it could have been much worse. Swarms of moon jellyfish attacked the refrigeration system of three nuclear power plants in Sweden, prompting emergency shut downs. Moon jellyfish "is 95% water and has no brain," says Gwynn. Sure. That probably means they are controlled by a spacefaring calamari civilization hiding behind the Sun. The day of the reckoning is near, people.